On-Line Defect Detection in Web Offset Printing

Abstract

This paper presents a detailed description of a vision system developed to detect and locate the nonuniformities that appear on the web offset printing machine. Specifically, the system is capable of monitoring the high-speed web offset printing in a real time environment and alerting the operator of any events (e.g., structural faults, color variations, missing characters, ink splashes, streaks, etc.) that disrupt the uniformities in the web offset printing. Such events are thought to affect crucial printing properties, resulting in non-uniformities in printing and impacting its quality and printability. This paper describes the vision system in terms of its hardware modules, as well as the image processing algorithms that it utilizes to scan the color images and locate areas of defect from the printing web. Basically, the system utilizes high-speed image scanning algorithms to detect edges and boundaries using linear and non-linear filters of dynamic size, threshold and transformation for further analysis. In addition to being tested in a laboratory environment, a prototype of this system was constructed and deployed to a web printing system, where its performance was evaluated under realistic conditions. The system was installed on a Flexo gravure-print-press machine for testing, and it was found that the vision system was able to successfully monitor and detect nonuniformities.

Assessing print quality by machine in offset colour printing

“…The system can recognise defects, categorise them into one of 47 classes, including colour drift, and suggest actions for the operator to eliminate the cause of defect. Another image analysis-based defect detection tool, assisting the press operator in finding defect in the print and taking appropriate adjustments, was tested on a Flexo gravure printing press [16,17]. The system is supposed to be used on offset printing presses.…”

Automatic Defect Detection for Web Offset Printing Based on Machine Vision

“…Automatic surface defect detection based on machine vision has been widely used in many industry fields, such as the semiconductor manufacturing industry [1][2][3], electronic industry [4], textile industry [5] and printing industry [6]. Especially in the printing industry, defect detection is indispensable to ensure the quality of the printed product.…”

“…For defect detection of web offset printing, research has rarely been conducted on this topic except reference [6,7]. The study in reference [6,7] is ground-breaking work.…”

Printing Defect Identification in Pharmaceutical Blisters Using Image Processing

“…The above technique is difficult for detecting patterns. High-speed image scanning algorithms can be used to detect edges and boundaries [5] for line defect detection in web offset printing. The above technique can detect nonuniformities that appear, but the image quality is slightly inferior when compared to other printing.…”